Method of manufacturing turbine blades



Sept 2, 1941.

s. s. S TINE METHOD OF MANUFACTURING TURBINE BLADES Filed Sept. 26, 19392 Sheets-Sheet 2 INVENTOR Sam/E1. S. STINE.

ATTORNEY Patented Sept. 2, 1941 UNlTED STATES PATENT OFFICE iun'rnon ormagggt'gunme TURBINE I 2 Samuel S. Stine. Lansdowne, Pa., assignor toWestinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application September 26, 1939, Serial No.296,567

2 Claims.

My invention relates to turbine blade manufacture and it has for anobject to provide an improved method of rolling so that bladesofdecidedly unsymmetrical section may be satisfactorily rolled. r

More particularly, my invention is concerned with rolling of stripmaterial which may be divided to provide vane or blade elements forturbines and the like and having 'a section such as disclosed andclaimed in Reissue Patent No. 18,485, vMay 31, 1932. It will be apparentthat theblade sectionshown in this patent diflfer'sfrom the ordinaryreaction and impulse sections in the relatively greater lack ofsymmetry. The standard impulse section is symmetrical, or nearly so, andthe usual reaction section, while unsym-- I metrical, is not so much soas the new section and it has sharp edges at both sides. These priorshapes or sections have been rolled; however, it was found with thesection of said patent, due-to the rounded blunt edge at one side andthe thin tapered edge at the other side, that rolling was notsatisfactory because of excessive side thrust and the tendency towaviness at the thin edge. In this connection, when rolling a singleunsymmetrical section, tremendous pressures have to be applied to .rolldown the thin edge, and the utilization of such pressures for thispurpose involves the imposition of end thrusts on the rolls.

In accordance with the present invention, the

aforementioned difficulties are avoided by roll- 9 ing a double stripand then slitting the latter.

When rolling double, the problem of end thrust on the rolls is notencountered, irregularity or waviness of the thin edge is avoided, and amore convenient and better relation of the passes with respect to therolls may. be secured. Stock of elongated cross-section is rolled in asuitable number of passes to form the double strip, the latter beingsevered or slit to form strips to be divided into blade sections. Whileeither hot or cold rolling may be employed, it is preferred to use acombination of hot and cold passes. The work is annealed and pickled insuitable relation tothe passes, annealing serving the usual purpose ofstress relieving and pickling that of scale or oxide removal. If coldrolling is depended upon, then it is necessary to anneal and pickle thedouble strip alternately with rolling passes or with two or more suchpasses. If the combination of hot and cold rolling is used, the blankmay be treated and passed through all hot passes without the necessityof reheating, or it maybe reheated if required: and, after going throughthe final hot pass, the shape is pickled, annealed,

and again pickled, after which it may be passed through one or more coldpasses to bumish and polish the surface. Preferably, suitable stock ofcircular cross section is used, the stock being heated and rolled toform a transversely elongated shape having curved edges and the shape isedge-rolled to secure uniformity in width and then rolled in a suitablenumber of passes toform a double strip, which, after annealing andpicklin is cold rolled and slit at the junction region of the thinedges. After severing of the double strip, the parts thereof are passedthrough straightening rolls to straighten the strip and to roll down anyburring at the thin edge. Accord- 111813. a further object of myinvention is to roll unsymmetrical blading by rolling a double bladestrip and then slitting the latter. I

A further object of my invention is to roll vane orblade strip ofunsymmetrical section by providinga shape of elongated section, edgerolling the shape to secure width uniformity, then rollingthe shape toform .a double blade or vane strip, and slitting the double strip toprovide blade or vane strips of the desired unsymmetrical section.

These and other objects are effected by my in-' vention as will beapparent from the following description and c1aims,-taken in connectionwith the accompanying drawings, forming a part of this application, inwhich: Fig. 1

Fig. 2 showsdiagrammatically a break-down pass for exfoliating scale; I

Fig. 3 is a diagrammatic view showing further flattening to provide ashape which is transversely elongated and curved at the edges;

Fig. 4 shows edge-rolling of the elongated shape to eflect uniformityinwidth;

Figs. 5, 6, and 7 show passes for forming the transversely elongatedshape into a double I line x1-xr of Fig. 10, showing the effect of thestraightening rolls in rolling down the thin edge of a strip;

Fig. '12 shows a strip sectioned for turbine blades; and,

is a fragmentary isometric view of .stock;

Fig, 13 shows a turbine blade employing one of the sections.

Referring to the drawings more in detail, as already pointed out, theinvention may be carried out by either cold or hot rolling, preferablyby a suitable number of hot and cold passes, to form a double strip. I fcold rolling is depended upon,

then the work must be pickled and annealed in suitable relation'to thepasses to obtain satisfactorily rolled blade material. Also, followingthe hot passes, the double strip should be pickled, annealed, andpickled before being subjected to cold rolling to give a burnished andpolished surface.

Preferably, a blank Iii-of circular cross-section, as indicated in Fig.1, is used. .With the blank heated to a suitable temperature, it isgiven a break-down pass between roll elements I4 and i5 largely for thepurpose of exfoliating scale, the broken-down blank being shown at Illain Fig. 2. Next, the blank is passed between roll elements Ila and i5a,as shown in Fig. 3, to provide the shape lilb of elongated sectionhaving convexlycurved edges i8. h

To overcome the effect of minor variations in diameter of the rod ID aswell as the extent of flat rolling, as shown in Figs. 2 and 3,.- and toassure of uniform sectional dimensions of the blade strip, the elongatedshape iOb is edgerolled to secure uniformity in width, Fig. 4 showingthe edge-roiled shape llic in relation to rolls b and IE1). Procurementin this way of width uniformity, any sectional area variations resultingin thickening, particularly toward the edges,

assures of adequate material for the passes hereinafter described withthe material positioned widthwise for minimum deformation or flow, anyvariations in thickness secured by edge-rolling being rolled out withelongation in subsequent passes. As the double strip to be rolled hasthick outer edges and joined thin edges, any bulging or thicknessvariation of the edge-rolled shape near verging to provide the sharpedge 25, the face 21 being convex and the face 22 being concave.

slitting or severing of the double strip may resuit in bending of theblade strips and the thin edge may be burred to some extent on accountof shearing. Therefore, as shown in Figs. '11 and 12, each strip 2 ispassed between straightening rolls, not only to effect straighteningthereof, but cooperating rolls 2! and 2| assure of rolling out anyburring at the thin edge.

- As shown in Fig. 12, each strip 24 is out into turbine blade sections3] and such sections, when suitably joined to packing pieces or rootelements 22, provide finished turbine blades, as shown in Fig. 13. Whilethe blade strip material is preferably used in the manufacture ofturbine blades, it will be obvious that such material may be employed inthe manufacture of any suitable blade or vane element arranged in a pathof fluid flow.

From the drawings, it will be noted that the junction region of thedouble strip I00 (Figure 8) is constituted by distinct angular portion32 formed by the angular rib 34 on the roll ii! cooperating with theangular groove 25 on the roll Hf, this rib-and-groove relation beingpreserved throughout the forming passage, as shown in Figures 5 to 8,inclusive,

What I claim is:

,1. The method of rolling strip for sectioning into turbine blades, saidstrip being of an unsymmetrical section having rounded blunt inlet andthin sharp outlet edges and curved faces merging into the rounded bluntedge and converging to provide the sharp edge, one of said faces beingconvex and the opposed face being concave, said method comprisingproviding stock of circular cross section; heating said stock, and whileheated, rolling it'to form a shape which is elonthe edges thereof istherefore positioned for deformation to the best advantage.

Preferably, hot rolling of the work,'without reheating, is continued,the edge-rolled elongated shape liic of Fig. 4 being rolled ina suitablenumber of passes to form the double strip. For

example, in Figs. 5, 6, and '1, there are diagrammatically shown pairsof opposed roll elements He and I50, lid and lid, and He and lie,forrolling the shape into the forms llid, Hie, and I01, respectively.The double strip iflf from the final hot pass is pickled, annealed, andagain pickled before being rolled cold between the roll elements MI andi5} shown in Fig. 8, for burnishing and polishing the surfaces toprovide the finished double strip ing.

The double strips iiig are passed between a pair of holding rolls 20 and2! and cooperating rotary shear elements 22 and 23, the rolls grippingone of the strip parts 24 and. shear elements 22 and 23 slitting orsevering the other part 24 therefrom along the common thin edge 25. Eachstrip part 24 has a rounded or blunt edge 26, curved faces 21 and 28merging into the convex surface defining the rounded blunt inlet edgeand con- ,gated transversely and has curved edges, rolling the shape bythe application of rolling pressure to the curved edges to secureuniformity of width, and then rolling the shape to form a double stripwherein a pair of strips are joined at their thin edges; and, when cold,cold-roiling the hot-rolled double strip .to provide burnished andsmooth blade surfaces and then severing the cold-roiled double strip toprovide separate strips.

2. The method of rolling strip for sectioning into turbine blades; saidstrip being of an unsymmetrical section having rounded blunt inlet andthin sharp outlet edges and curved faces merging into the rounded bluntedge and converging to provide the sharp edge, one of said faces beingconvex and the opposed face being concave; said method comprisingproviding stock of circular cross section; heating said stock, and,while heated, rolling it to form a shape which is transversely elongatedand has curved edgespand while heated, rolling said shape in a suitableI section thereof and to provide burnished and smooth blade surfaces;and slitting the coldrolled strip to provide separate strips.

SAMUEL s. S'IINE.

